This invention relates to guide bars for chain saws that support and guide saw chain in the cutting of trees and more particularly to such guide bars that simultaneously treat the resultant tree stump with fungicide.
When cutting a tree, e.g., with a tree harvester equipped with a chain saw, the resultant tree stump has an exposed surface that is susceptible to fungus growth. The fungus is harmful to forest vegetation and it is accordingly desirable to prevent such growth by the application of a fungicide to the exposed surface of the stump. The procedure commonly used for application of the fungicide is to provide the guide bar for cutting chain with conduit and outlet holes that extend substantially the length of the bar through which a liquid fungicide is flowed under pressure from the guide bar onto the stump. Such procedures are most commonly used by tree harvesters (a tractor-like machine having a maneuverable grapple and chain saw).
A tree harvester typically severs a large tree, e.g., 10-20 inches in diameter in about a second and in that time, the liquid treatment has to be applied over the newly exposed surface of the stump. To achieve the intended result in such a short time span, the fungicide has to be liberally applied under pressure.
There are a number of problems with the procedures currently in use. The cost of the guide bar is significantly increased. The application of the liquid fungicide is messy with much of the fungicide wasted when liberally applied. There is also a concern that the over spraying of the fungicide can itself create an environmental concern. Still further, the procedures that are in use, even with liberal spraying, do not adequately cover the exposed surface of the tree stump.
The problem with inadequate surface coverage is believed to be caused by several factors. The liquid fungicide is connected into the bar adjacent the rear end of the bar and then directed through a perforated conduit toward the distal end of the bar. The pressure drops as the liquid moves through the conduit and a greater amount of the liquid is forced out of the holes closest to the rear end. The cutting action of the bar is pivotal and the configuration of the tree is circular. Thus, as the bar and chain cut through the tree, the rear end of the bar does the least amount of cutting and traverses the smallest area of the exposed surface of the tree stump and yet, as explained, it receives the greatest flow of the fungicide.
A further factor is that the holes or perforations are necessarily spaced along the bar length and the bar face wherein the conduit resides is close to or in sliding contact with the exposed surface of the tree trunk. Thus the liquid is applied as spaced apart streaks or strips substantially the width of the hole opening leaving intermediate bands of the trunk surface that does not receive the fungicide.
The present invention addresses these factors. In the preferred embodiment, the perforations in the conduit are formed into xe2x80x9chole formsxe2x80x9d having a frusto conical shape that is directed inwardly. Thus the wall of the conduit immediately surrounding the opening is inset toward the interior of the conduit and thus spaced further from the surface being treated. This allows the liquid treatment material flowing out of the opening to spread before being deposited on the tree trunk surface. The inset is projected into the linear flow of the material being flowed through the conduit producing turbulence which further aids in the spreading of the fungicide as it exits the openings/perforations. As a further improvement or embodiment, the openings in the conduit may be strategically increased in size back end to distal end which may provide a more even application of the fungicide across the surface of the tree stump.
The conduit as described is preferably provided in a solid bar as differentiated from a laminate bar wherein a sufficiently dimensioned channel can be produced along the length of the bar (on one or both sides). A tube of soft metal is inserted in the channel. The hole forms are produced in the tube by piercing the tube at the desired spacings. The piercing operation (for the soft metal of the tube) is readily accomplished using a needle tool which will indent the tube wall surrounding the opening as well as generate the desired size of opening. Examples of soft metal for the tube are copper, brass and aluminum. Such piercing of soft metal also enables easier provision of different hole sizes along the bar length as may be provided in the further embodiment of the invention.
The invention and the benefits achieved will be more fully appreciated upon reference to the following detailed description having reference to the accompanying drawings.